Heterologous production of α-Carotene in Corynebacterium glutamicum using a multi-copy chromosomal integration method

The carotenoid, α-carotene, is very beneficial for human health and wellness, but microbial production of this compound is notoriously difficult, due to the asymmetric rings on either end of its terpenoid backbone. Here, we report for the first time the efficient production of α-carotene in the industrial bacterium Corynebaterium glutamicum by using a combined pathway engineering approach including evaluation of the performance of different cyclases and analysis of key metabolic intermediates to determine flux bottlenecks in the carotenoid biosynthesis pathway. A multi-copy chromosomal integration method was pivotal in achieving stable expression of the cyclases. In fed-batch fermentation, 1,054 mg/L of α-carotene was produced by the best strain, which is the highest reported titer achieved in microbial fermentation. The success of increased α-carotene production suggests that the multi-copy chromosomal integration method can be a useful metabolic engineering tool for overexpression of key enzymes in C. glutamicum and other bacterium as well.